The growing popularity of prepared foods, particularly fresh produce and frozen and dried foods, has expanded the need for improved food processing equipment. Processing fresh foods commonly involves cleaning, dewatering and drying the foods before they undergo further processing and packaging. Conventional conveyor based dewatering systems used in the food processing industry draw water off the food products as they travel down a conveyor belt. The WaterVac.RTM. water removal systems sold by Rey Industries, Inc., the owner of the present invention, utilize one or more suction plenums placed directly under the dewatering conveyor belt to draw water off a variety of food products. The WaterVac.RTM. system may also include a blower or pressurized plenum above the conveyor belt opposite the suction plenum to facilitate the removal of water from the food products.
The apparatus for preparing raw potato slices described in U.S. Pat. No. 4,251,895 issued to Caridis et al., uses an air pressure plenum located above the conveyor belt in conjunction with air suction below the belt to remove water and unwanted particles from potato slices. The air pressure plenum described in the Caridis patent is designed to supply a "blast" of air against the conveyor belt through slit orifices by the side walls of the plenum and a baffle plate. This blast of air is said to place the potato slices in a turbulent or dancing state to facilitate the removal of potato particles from the slices and from the atmosphere around the slices as they are driven airborne. While such a system may tend to improve the dewatering process for potato slices, the use of a high velocity blast of air is not well suited to more light weight or fragile food products.
The present invention was developed as part of an effort to improve conventional processes for dewatering fresh cut lettuce after it has been washed.
Presently, lettuce is spin dried in large centrifugal spin tanks. Spin drying tends to bruise the lettuce. This bruising, in turn, accelerates the rate at which the lettuce degrades and accounts for much of the brown lettuce seen in the bags of fresh cut lettuce in grocery stores.